Cameron Crowe, prosecuting, said streaming devices were not illegal if they were used to access free content.

He said: "If, however, they are designed, produced or adapted for the purpose of gaining unauthorised access to copyright content or subscription services - such as Sky and BT Sports - they become illegal."

Mr Crowe said a piece of software known as Kodi led the devices to be known as Kodi boxes.

Brian Thompson's shop in Middlesbrough, where he advertised that he sold set-top TV boxes that allowed people to watch Premier League matches and movies for free (Image: Trading Standards /PA Wire)

He said: "Kodi boxes are not illegal per se. However, they allow a person to install add-ons, some of which allow unauthorised access to copyright and subscription material.

"Devices with those add-ons installed at the point of sale have become known as fully or pre-loaded devices."

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He said he was suspending Thompson's jail sentence but others in the future may not be so fortunate.

Paul Fleming, defending, said his client was a hard worker who had succeeded and failed in businesses over the years.

Thompson, of Barnaby Avenue, Middlesbrough, admitted one count of selling and one count of advertising devices "designed, produced or adapted for the purpose of enabling or facilitating the circumvention of effective technological measures".

Industry experts believe more than one million Kodi boxes have been sold.